In digital AV signal transmission systems in conformity with the DVI (Digital Visual Interface) standard, the HDMI (High-Definition Multimedia Interface) standard, and the like, a digital AV signal in which video data and audio data are multiplexed is serially transmitted. Digital signal receivers decode received a digital AV signal, and further, separate the digital AV signal into video data and audio data, which are in turn output. Audio data is typically overlaid, in the form of packets, on blanking intervals of video data. An audio data processing section in the digital signal receiver converts audio data in the form of packets into audio data in the form of a stream, which is in turn output. Also, a video data processing section in the digital signal receiver performs a process, such as format conversion or the like, with respect to the separated video data, and outputs the processed video data.
Also, in the digital AV signal transmission system, a clock signal is transmitted in a transmission line separated from an AV signal transmission line. The digital signal receiver generates its own operation clock signal from the given clock signal.
On the other hand, there is a digital signal receiver which comprises a plurality of signal receiving sections each receiving a digital AV signal and a clock signal and can receive a plurality of channels of digital AV signals. Such an apparatus typically comprises a selection section for selecting any one of a plurality of channels of digital AV signals and clock signals. A video data processing section and an audio data processing section process video data and audio data of a channel selected by the selection section. In other words, each signal receiving section is exclusively used.
Regarding conventional packet receivers which receive encrypted packets, when a received packet is not encrypted, power supply to a decoding means for decoding packets is paused, thereby reducing power consumption in the apparatus (see, for example, Patent Document 1).    Patent Document 1: Japanese Patent Unexamined Publication No. 2000-261497 (page 4, FIG. 1)